The present disclosure relates generally to type selective and polarization selective device(s) for Raman spectroscopy.
Raman spectroscopy is used to study the transitions between molecular energy states when photons interact with molecules, which results in the energy of the scattered photons being shifted. The Raman scattering of a molecule can be seen as two processes. The molecule, which is at a certain energy state, is first excited into another (virtual) energy state by the local electromagnetic field, which is ordinarily in the optical frequency domain. The excited molecule then radiates as a dipole source under the influence of the environment in which it sits at a frequency that may be relatively low (i.e., Stokes scattering), or that may be relatively high (i.e., anti-Stokes scattering) compared to the excitation signal. In some instances, the Raman spectrum of a given material shows multiple pairs of Stokes/anti-Stokes peaks. For each pair, the frequency difference between the excitation signal and the Stokes signal is the same as that between the anti-Stokes signal and the excitation signal. While Raman scattering is very useful, the magnitude of Raman scattering is typically very low. Furthermore, the polarization of the Raman signal is ordinarily random unless otherwise influenced by the environment.